View Full Version : New Ceiling
22nd Aug 2008, 07:01 AM
I am in the process of plastering the ceiling under the extension I have built which will become the kitchen/dining room. I have used CSR Superceil 10mm glued and screwed. As you can see by the framework the trusses change direction so I would be creating a patchwork job if to use the rule of 90 deg offset to fixing. Given the Superceil can span 600mm (truss space the same) It didnt really which dierection i put up so I chose the one which minimises the joints. I am now in the process of joining them and I have bought the good ol CD from Bunnings which shows the way to do walls. I am using the perforated paper tape and using the premixed total joint cement as base coat 2nd coat and topping coat for the final.
I found laying a base coat between the joins and then putting the paper on follwed by a thin coat using 100mm worked o.k but I had to cut the paper and put in a couple of new ones as i got a couple of bubbles. Is is best to wet this tape first?? as it doesnt seem too absorbent.
I then used the good old orbital sander (to create a dust storm and a half :doh:) and the joins look pretty good and I have ended up with a flush finish. I was looking at painting over them but now on closer inspection going to finish off with a curved join using a 250mm curve.
I am using a plastic 250mm curve knife and note they are quite flexible should I use this at 90deg to get the curve or more like 45 deg? just using the 45deg doesnt get enough of the plaster over the joins as it spreads. Or should i do a couple of coats?
Here are some pics of the job.
22nd Aug 2008, 11:17 AM
I am very much the amateur so take this as being from my experience only.....I cut the paper to length and soak it in a bucket of water, squezzing out excess by dragging it between by fingers before pressing into a thin bed of compound in the joint and then overlaying more compound.
I never did any good with the 250mm spatulas with the curved blade as these only allow a straight draw along the length of the join which I always buggered up somehow. My preference now is to use a straight edged spatula in a criss cross pattern across the joint spreading out to about 150mm on the first coat and 250-300mm wide on the top coat.
This only needs 2 coats after the initial tape application layer and each does not need to be very thick. Aim to make each as smooth as you can reasonably get and you only need a light hand sand on the final coat to feather the edges to the plasterboard paper.
I used a sander on my first couple of goes where I was in a hurry and probably put on too much compound and did not allow enough time to dry properly. It is a lot easier and cleaner if you take your time to get the coats reasonably smooth and allow time for them to dry and then just lightly hand sand the top coat.
22nd Aug 2008, 05:54 PM
Don't soak the tape it makes it harder to use just follow the tips on this video and you will have no problems.
Throw away and plastic tools and for a few $ go and buy proper steel blades to get a good result. Flat not curved. You cant get into too much trouble with a flat blade but you can get into plenty with a curved one. I think I need to get on and finish a few of my video's to show 2nd coating and top coating I think. It is much easier to show the best methods rather than try and explain them.
As for the hip roofs creating 2 way trusses, the builder has to trim out between the trusses with noggins at the corect centers for the board type being used. So that the board can all be run in one direction and fixed according to the manufactureres specs.
YouTube - How to tape in a plasterboard join using paper tape
23rd Aug 2008, 11:27 AM
:whs: Rod knows his stuff - watch & learn. . . :U :2tsup:
24th Aug 2008, 01:13 PM
Sorry to hijack but Rod, does this work with ceilings that already been painted as well? In our loungeroom and kitchen, you can see a slight groove where the plasterboards have joined. I was wondering should i use this techique to smooth out the grooves? And do i need to sand back the paint?
24th Aug 2008, 08:25 PM
Sounds like the slight grooves you mentioned are the edges of the rebate of a join that has been under filled.
To fix this you can go over the top with top coat and sand back. Use a 12" (300mm) flat blade. I will get a round to posting a video on you tube about applying top coat in a way that gives you a flat join every time. It is a bit hard to explain by typing. But the general idea is to put on a heavy but consistant coat, cut back the edges then cut back the excess through the center with the blade at about a 45 deg angle off the join. Then run though the join with the blade very flat to the join.
ARGGGHHH I know this doesnt make a lot of sense. My writing skills evade me in describing this very important method. I will try to get a video done soon, been busy with other things lately.
You can go to my web site and get my phone number and call me if you like and I can give you a better explaination. I dont mind a bit, but please guys ONLY if you REALLY need too.
25th Aug 2008, 08:19 AM
Thanks for that Rod. I think i understand what you are trying to say. I'm not in any hurry so i'll wait for the video
25th Aug 2008, 05:06 PM
Thanks, I'm keen to give it a go for the final coat I have a trusty 280mm new blade flat, (I was going to put a 3mm curve in it as it was only $20 bucks but will now give it a go with the flat blade.) It is definitely more challenging doing it overhead as both the vids show it on an wall join.
My ceiling is 9ft so balancing on the work plank makes it more challenging.:o I notice the joining material on the vids seems to be a bit more consistant than the pre mixed stuff ? Why when you pack it on to get it to stick overhead and in the process of smoothing you get tiny air bubbles and it takes some convicing to get them out without leaving it for sander to fix.
Are we aiming for a flat finish over a 300mm spread or as you describe a lump in the middle and then spread off each side 45 deg then scoop off the excess in a flat motion. What length should be considered work space 1m at a time or 500mm at a time....
25th Aug 2008, 06:31 PM
The length you do will be what you are comfortable with.
If the surface is painted it is next to impossible to get the air bubbles out. If not try flattening out the blades and use a lot of pressure without taking away any material.
26th Aug 2008, 07:43 AM
As time goes on I have been trying a few techniques, I found putting the stuff on and then smoothing across the join then down the join seems to work best. The more times you touch the stuff it doesn't like it and becomes "worked". When you give it a final smooth, the hardest part is going over the joint without one of the ends of the trowel leaving a line. I am obviously trying to reduce the amount of sanding over the area. I dont want to try and put some down with heaps of pressure to get a flat finish and digging into the cardboard of the gyprock.
As you can see from the early photo it is not painted, but after a couple of smooths you can get the bubbles out especially with the top coat as it seems to be a lot easier to work with. What should the finish product look like after top coat? an area 300mm wide blended into the new gyprock or slightly bigger?
26th Aug 2008, 06:15 PM
The topcoat should end up around 300mm wide and the edges "feathered" off.
The method you mention is called cross trowelling which is not a bad method for the initial application of the mud, for someone not skilled. With the final run through the trowell or blade should be held quite flat so that it willnot dig in to the board. You will always end up with a trowell off mark where you lift the blade from the join that needs to be sanded. If the join is flat and the width of the blade you will not get any trowel lines down the join.
2nd Sep 2008, 12:19 PM
Here is a couple of pics, where I see this job now ready for an undercoat of paint. There is still more joining work to do on the right of photo, when I remove the whole wall and continue on. I have a couple of close up pics to show a bit of the detail. I am quite happy when I run my hand across the join and it appears that I have a flat finish and once the paint goes on then the join should be invisible? :cool:
Tell me if there is a slight colour patch between 2nd and topcoat, where you can just make out some of the 2nd base coat is o.k.
Getting picky here, I was actually considering using no topcoat, is this recommended? As the joint seemed to be quite flat. I have dusted off a few times, any final comments?
2nd Sep 2008, 04:09 PM
You must use top coat.
It is very hard to comment on a join from a photo however I would point out that the edges look like they need more sanding. It doesn't matter if the base coat shows through the top coat, provided that as soon as this happens you should not sand any more as you will only sand the top coat away.
If you have a "bump" of basecoat the best thing to do is to scrape it back flat, put a skim coat of top coat over then sand again.
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